Today's hard disk drive products utilize disks that comprise rigid substrates. The substrates may comprise rigid materials such as aluminum, glass, and ceramics. It is well known in the art that when a disk that comprises a rigid substrate is rotated at a high speed, it will exhibit a certain amount of disk flutter and rotational run-out. In the prior art disk, because the disk is rigid, the disk flutter and rotational run-out is relatively small. In the prior art, disk flutter and rotational run-out causes the formation of aerodynamic turbulence over the surfaces of the rotating disk; however, because the disk is rigid, the aerodynamic turbulence is also relatively small.
Before actual shipment of a disk drive, it is desirable to characterize the components comprising the disk drive. In a disk drive that utilizes flying head technology, characterization of the components includes characterization of the flying heads. The need for characterizing flying heads stems from the fact that if a flying head is manufactured with non-optimal dimensions and/or quality, its ability to fly may be adversely affected by the aerodynamic turbulence over a rotating disk. Electrical and/or optical components on the flying head may further enhance the effects of the aerodynamic turbulence. Thus, it is desirable to measure and characterize flying heads to determine how their dimensional characteristics and/or quality may be affected by aerodynamic turbulence prior to their inclusion in a finally assembled disk drive product.
While the dimensional characteristics and/or quality of a flying head may be sufficient to maintain the flying head over a rotating disk that comprises a rigid substrate, they may not be adequate enough to maintain the flying head in a flying condition over a disk that exhibits increased amounts of disk flutter and/or rotational run-out.
In the prior art, flying heads are typically characterized during a test procedure that is conducted prior to final assembly of the disk drive. The characterization test utilizes monochromatic multi-beam interference based test instrumentation to measure the fly height between a flying head and a clear smooth rotating glass test disk. In the prior art, the test disk is designed to exhibit the same properties as that of the rigid disks used in the finally assembled disk drive. Unfortunately, this prior art approach does not characterize flying heads for use over disks that may exhibit increased amounts of flutter and/or run-out.
Thus, what is needed is a method and apparatus for measurement and characterization of flying heads for use over disks that comprise non-rigid substrates and over disks that exhibit properties such as increased amounts of flutter and/or rotational run-out.